It is well known in the art of beverage containers to make drink pouches constructed from flexible panels cut from sheets of laminate web materials which are welded together on all but one side, filled with a beverage and then the remaining open side is sealed. In order to drink the contents from such pouches, the user must either tear off a corner of the pouch or insert a drinking straw through the web material into the storage compartment of the pouch. Since the laminate web material may be made with layers including PE (polyethylene) for sealing, Al (aluminum) for air and moisture barrier, and Bonyl (bioriented nylon) for strength, it is no easy matter to pierce it with a common plastic drinking straw, especially for children, the largest segment of the consumer population for such products.
One of the greatest problems is that of opening the hole by means of the straw in a simple, neat manner. Especially in the case of containers which were filled and sealed when the liquid contents were in a hot state, problems arise upon introduction of the straw, since vapour present in the empty head space of the container condenses upon cooling so that there is hardly any air left in the head space. One consequence thereof is that the liquid level may rise and the piercing hole may be below the top of the liquid, resulting in undesirable liquid discharge upon normal opening of the container. Additionally, due to the fact that the front and rear sides of a beverage container are located relatively close to each other, careless piercing may risk piercing the rear side of the beverage container.
Suggested constructions for beverage containers are taught by DE-OS 4140540A1 and U.S. Pat. No. 5,868,658. These patents teach the construction of a bag in which a piercing hole is provided at the time of manufacture by punching through all the layers of the front panel sheeting. The inside of the front side sheeting has a closure sheeting strip (or patch) welded thereto around or on the piercing hole, so that a tight closure is formed. However, the disclosed methods are wasteful and require added welding steps and apparatus to the assembly operation.
A method of making a beverage packaging bag which uses a laser source to facilitate piercing of a straw through the panel is taught in U.S. Pat. No. 4,762,514. The patent teaches providing the panel segment with a pattern of score lines in a portion of the reinforcing outer layer by means of a single application of a laser which is directed at the bag through a mask. The mask shapes the beam to form the desired pattern of score lines.
U.S. Pat. No. 3,790,744 to Bowen, discloses the use of laser energy to provide a straight weakened line in the laminate web materials as to form a tear line across a length of the laminate. However, the depth of the weakened area is intended to be uniform in order to form a straight tear line, not focussed to facilitate puncturing with a straw.